/*+
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 * Copyright (c) 2001, 2010, Oracle and/or its affiliates. All rights reserved.+
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.+
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 *+
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 * This code is free software; you can redistribute it and/or modify it+
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 * under the terms of the GNU General Public License version 2 only, as+
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 * published by the Free Software Foundation.+
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 *+
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 * This code is distributed in the hope that it will be useful, but WITHOUT+
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or+
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License+
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 * version 2 for more details (a copy is included in the LICENSE file that+
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 * accompanied this code).+
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 *+
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 * You should have received a copy of the GNU General Public License version+
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 * 2 along with this work; if not, write to the Free Software Foundation,+
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 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.+
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 *+
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 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA+
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 * or visit www.oracle.com if you need additional information or have any+
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 * questions.+
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 *+
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 */+
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+
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#include "precompiled.hpp"+
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#include "runtime/atomic.inline.hpp"+
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#include "runtime/thread.inline.hpp"+
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#include "runtime/threadCritical.hpp"+
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+
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// OS-includes here+
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# include <windows.h>+
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# include <winbase.h>+
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+
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//+
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// See threadCritical.hpp for details of this class.+
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//+
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+
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static bool initialized = false;+
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static volatile jint lock_count = -1;+
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static HANDLE lock_event;+
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static DWORD lock_owner = -1;+
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+
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//+
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// Note that Microsoft's critical region code contains a race+
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// condition, and is not suitable for use. A thread holding the+
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// critical section cannot safely suspend a thread attempting+
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// to enter the critical region. The failure mode is that both+
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// threads are permanently suspended.+
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//+
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// I experiemented with the use of ordinary windows mutex objects+
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// and found them ~30 times slower than the critical region code.+
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//+
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+
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void ThreadCritical::initialize() {+
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}+
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+
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void ThreadCritical::release() {+
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  assert(lock_owner == -1, "Mutex being deleted while owned.");+
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  assert(lock_count == -1, "Mutex being deleted while recursively locked");+
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  assert(lock_event != NULL, "Sanity check");+
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  CloseHandle(lock_event);+
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}+
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+
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ThreadCritical::ThreadCritical() {+
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  DWORD current_thread = GetCurrentThreadId();+
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+
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  if (lock_owner != current_thread) {+
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    // Grab the lock before doing anything.+
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    while (Atomic::cmpxchg(0, &lock_count, -1) != -1) {+
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      if (initialized) {+
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        DWORD ret = WaitForSingleObject(lock_event,  INFINITE);+
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        assert(ret == WAIT_OBJECT_0, "unexpected return value from WaitForSingleObject");+
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      }+
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    }+
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+
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    // Make sure the event object is allocated.+
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    if (!initialized) {+
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      // Locking will not work correctly unless this is autoreset.+
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      lock_event = CreateEvent(NULL, false, false, NULL);+
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      initialized = true;+
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    }+
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+
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    assert(lock_owner == -1, "Lock acquired illegally.");+
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    lock_owner = current_thread;+
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  } else {+
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    // Atomicity isn't required. Bump the recursion count.+
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    lock_count++;+
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  }+
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+
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  assert(lock_owner == GetCurrentThreadId(), "Lock acquired illegally.");+
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}+
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+
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ThreadCritical::~ThreadCritical() {+
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  assert(lock_owner == GetCurrentThreadId(), "unlock attempt by wrong thread");+
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  assert(lock_count >= 0, "Attempt to unlock when already unlocked");+
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+
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  if (lock_count == 0) {+
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    // We're going to unlock+
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    lock_owner = -1;+
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    lock_count = -1;+
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    // No lost wakeups, lock_event stays signaled until reset.+
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    DWORD ret = SetEvent(lock_event);+
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    assert(ret != 0, "unexpected return value from SetEvent");+
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  } else {+
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    // Just unwinding a recursive lock;+
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    lock_count--;+
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  }+
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}+
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